Flow is a PHP-based, strongly typed ETL (Extract, Transform, Load) and asynchronous data processing framework with low memory consumption thanks to its generator-based architecture.
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Supported PHP versions: 
Thanks to its rich collection of adapters, Flow can read and write data between sources and destinations while applying defined transformations on the fly.
<?php
declare(strict_types=1);
use function Flow\ETL\Adapter\Parquet\{from_parquet, to_parquet};
use function Flow\ETL\DSL\{data_frame, lit, ref, sum, to_output, overwrite};
use Flow\ETL\Filesystem\SaveMode;
require __DIR__ . '/vendor/autoload.php';
data_frame()
->read(from_parquet(__DIR__ . '/orders_flow.parquet'))
->select('created_at', 'total_price', 'discount')
->withEntry('created_at', ref('created_at')->cast('date')->dateFormat('Y/m'))
->withEntry('revenue', ref('total_price')->minus(ref('discount')))
->select('created_at', 'revenue')
->groupBy('created_at')
->aggregate(sum(ref('revenue')))
->sortBy(ref('created_at')->desc())
->withEntry('daily_revenue', ref('revenue_sum')->round(lit(2))->numberFormat(lit(2)))
->drop('revenue_sum')
->write(to_output(truncate: false))
->withEntry('created_at', ref('created_at')->toDate('Y/m'))
->saveMode(overwrite())
->write(to_parquet(__DIR__ . '/daily_revenue.parquet'))
->run();$ php daily_revenue.php
+------------+---------------+
| created_at | daily_revenue |
+------------+---------------+
| 2023/10 | 206,669.74 |
| 2023/09 | 227,647.47 |
| 2023/08 | 237,027.31 |
| 2023/07 | 240,111.05 |
| 2023/06 | 225,536.35 |
| 2023/05 | 234,624.74 |
| 2023/04 | 231,472.05 |
| 2023/03 | 231,697.36 |
| 2023/02 | 211,048.97 |
| 2023/01 | 225,539.81 |
+------------+---------------+
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